1. Field of the Invention
The present invention relates to a vibrating gyroscope and more particularly to a vibrating gyroscope which is used in a video camera for prevention of hand shaking or is used in a car-navigation system, a pointing device or the like.
2. Description of the Related Art
A first conventional vibrating gyroscope is disclosed in Japanese Unexamined Patent Publication No. 7-332988 and will be described with reference to FIG. 9.
As shown in FIG. 9, the first conventional vibrating gyroscope is designated by the reference numeral 100 and includes a vibrator 101. The vibrator 101 is made up of a first piezoelectric substrate 103 polarized in the thickness direction and a second piezoelectric substrate 104 polarized in the opposite direction to the first piezoelectric substrate 103, which are bonded and integrated through an intermediate electrode 105. The vibrator 101 further includes two divided electrodes 106a, 106b provided on one main face of the first piezoelectric substrate 103 so as to be spaced along the longitudinal direction of the first piezoelectric substrate 103, and a common electrode 107 formed on the entire one main face of the second piezoelectric substrate 104.
In the case of the vibrator 101, an oscillation circuit 130 as a driving means is connected between the common electrode 107 and the divided electrodes 106a, 106b. A detection circuit is connected to the divided electrodes 106a, 106b. When a driving signal is applied by the oscillation circuit 130, the vibrator 101 vibrates under a bending mode, and a detection signal in correspondence to a rotation angular velocity of the vibrator 101 is produced between the divided electrodes 106a, 106b, and supplied to the detection circuit 140.
Japanese Unexamined Patent Publication 7-332988 also discloses a vibrating gyroscope as shown in FIG. 10.
This second conventional vibrating gyroscope 110 includes a vibrator 111. The vibrator 111 is made up of a first piezoelectric substrate 113 polarized in the thickness direction and a second piezoelectric substrate 114 polarized in the same direction as the first piezoelectric substrate 113, which are bonded and integrated through an intermediate electrode 115. The vibrator 111 further includes first two divided electrodes 116a, 116b provided on one main face of the first piezoelectric substrate 113 so as to be spaced along the longitudinal direction of the first piezoelectric substrate 113. Two second divided electrodes 117a, 117b are provided on one main face of the second piezoelectric substrate 114 spaced in the longitudinal direction of the second piezoelectric substrate 114.
In the case of the vibrator 111, an oscillation circuit 130 as a driving means is connected between one 116a of the first two divided electrodes and the intermediate electrode 115 and between the intermediate electrode 115 and one 117b of the second two divided electrodes. A detection circuit 140 is electrically connected between one 116a of the first two divided electrodes and one 117b of the second two divided electrodes. The other 116b of the first two divided electrodes and the other 117a of the second two divided electrodes are electrically connected to each other. When a driving signal from the oscillation circuit 130 is supplied, the vibrator 111 vibrates under a bending mode, and detection signals in correspondence to a rotation angular velocity of the vibrator 111 are produced between the first two divided electrodes 116a, 116b and between the second two divided electrodes 117a, 117b. The signal composed of the detection signal produced between the first two divided electrodes 116a, 116b and the detection signal produced between the second two divided electrodes 117a, 117b is detected by the detection circuit 140.
The conventional vibrating gyroscopes explained above have had the following problems.
In the case of the conventional vibrating gyroscope 100, the bending displacement of the vibrator is half of that of the vibrator of the conventional vibrating gyroscope 110, when the applied driving voltages are equal. The bending displacement has a correlation to the sensitivity of a vibrating gyroscope. As the displacement is larger, so the sensitivity is higher. Thus, the vibrating gyroscope 100 has a lower sensitivity than the vibrating gyroscope 110.
For miniaturization of a vibrating gyroscope, it is necessary to reduce the size of the vibrator. However, reduction of the size of the vibrator causes the sensitivity of the vibrating gyroscope to be reduced. To counteract this, the voltage could be made higher to obtain a higher sensitivity. Recently, however, there has been a greater demand for application of low voltage devices in the vibrating gyroscope market. Accordingly, it is unreasonable to increase the voltage. Thus, there has been a problem in recent years to construct a vibrating gyroscope in which the vibrator can be miniaturized and have a sufficient sensitivity.
By utilizing the vibrating gyroscope 110 of which the bending displacement is twice as much as that of the vibrating gyroscope 100, it is possible to construct a vibrating gyroscope which can-be miniaturized and have a sufficient sensitivity as described above. However, for the vibrating gyroscope 110, it is necessary to connect electrically the intermediate electrode 115 to an external oscillation circuit and so forth. Generally, the intermediate electrode 115 is led out by a lead wire soldered at a side face or an end face of the vibrator 111. However, it is very troublesome to solder a lead wire onto the intermediate electrode 115, since the intermediate electrode 115 is a very thin layer, and the piezoelectric substrate and solder have poor adhesive properties. It has been difficult to put the vibrating gyroscope 115 to practical use.